This application is based upon and claims priority from Japanese Patent Application No. 2000-11408, filed Jan. 20, 2000, the contents being incorporated therein by reference, and is a continuation of PCT Application No. PCT/JP01/00366, filed Jan. 19, 2001.
The present invention relates to a cooling system for a liquid-cooled internal combustion engine appropriately used for a cooling system for, for example, a water-cooled internal combustion engine mounted on an automobile.
Japanese Unexamined Patent Publication No. 5-231148 discloses a conventional cooling system for controlling a temperature of coolant of a liquid-cooled internal combustion engine to an appropriate value. As shown in FIG. 6, in the radiator circuit 210 by which coolant is circulated from the liquid-cooled internal combustion engine 100 to the radiator 200 and also in the bypass circuit 300, there are provided a pump 500, which is operated independently from the liquid-cooled internal combustion engine 100, and a flow control valve 400. The pump 500 and the flow control valve 400 are controlled by the control means (electronic control unit) 600 according to the temperature Tw2 of the coolant at the inlet to the liquid-cooled internal combustion engine 100 and the temperature Twc of the coolant at the outlet and also according to the state of a load given to the liquid-cooled internal combustion engine 100.
Due to the foregoing, according to the load given to the liquid-cooled internal combustion engine 100 such as during warm-up, a light load or a heavy load, the flow rate of the discharge from the pump 500 and the degree of opening of the flow control valve 400 are controlled so that the temperature of the coolant can be optimized.
However, in the above system, the operation is conducted as follows. For example, in the case where a heavy load is given to the internal combustion engine, the temperature of the coolant is controlled so that it can be lowered. Therefore, the degree of opening of the flow control valve 400 and the duty ratio (or rotational speed) of the pump 500 are raised so that the flow rate of coolant flowing in the radiator 200 can be increased and the radiating effect can be increased. In general, the influence of the change in the flow rate in the radiator 200 upon the change in the radiating effect of the radiator 200 is decreased as the flow rate in the radiator is increased. Therefore, even if the flow rate in the radiator is increased so as to try to lower the temperature of coolant, in the case that the flow rate in the radiator is already considerable high, the radiating effect is not so increased for the increase in the flow rate in the radiator. Accordingly, a rate of the cooling effect with respect to the pump work (power consumption) of the pump 500, which is necessary for circulating coolant to the radiator 200, is decreased. As a result, the unnecessary pump work is increased.
The blower 230 is controlled in such a manner that it is only turned on and off by the coolant temperature switch 231, which is insufficient to optimize the cooling effect.
The present invention has been accomplished to solve the above problems. It is an object of the present invention to provide a cooling system for a liquid-cooled internal combustion engine in which the cooling effect determined by the combination of a pump with a blower is optimized according to the state of a load given to the liquid-cooled internal combustion engine so that the necessary cooling effect can be obtained from the pump and the blower and, at the same time, the power consumption can be reduced.
In order to accomplish the above object, the present invention adopts the following technical means.
An embodiment of the present invention is a cooling system for a liquid-cooled internal combustion engine comprising: a radiator (200) from which coolant flows toward a liquid-cooled internal combustion engine (100) after the coolant flowing out from the liquid-cooled internal combustion engine (100) has been cooled in the radiator (200); a pump (500) for circulating coolant being operated independently from the liquid-cooled internal combustion engine (100); a blower (230) for blowing air to the radiator (200); a control means (600) for controlling the operations of the pump (500) and the blower (230), wherein the control means (600) determines the combination of the cooling effect of the pump (500) and that of the blower (230) for satisfying the necessary cooling effect according to a load given to the liquid-cooled internal combustion engine (100), and also the control means (600) controls the pump (500) and the blower (230) so that the sum (Lc) of the power consumption of the pump (500) and that of the blower (230) can be substantially minimized.
In another embodiment of the present invention, the control means (600) further comprises: a first map for determining a target coolant temperature (Tmap) determined according to a load given to the liquid-cooled internal combustion engine (100); and a second map for determining quantities of control of the pump (500) and the blower (230) so as to make the temperature of coolant converge upon the target coolant temperature (Tmap), wherein a flow rate of discharge from the pump (500) and a quantity of air blown by the blower (230) are controlled by the quantities, for control of the pump (500) and the blower (230), which are determined by the second map, and wherein the sum (Lc) of the power consumption of the pump (500) and that of the blower (230) is substantially minimized, and wherein feedback control is conducted so that the temperature of coolant becomes the target coolant temperature (Tmap).
In the above embodiment of the present invention, according to the state of a load given to the liquid-cooled internal combustion engine (100), the temperature of coolant to be controlled is determined, and the combination of the necessary cooling effect of the pump (500) and that of the blower (230) is determined. Therefore, the temperature of coolant can be appropriately controlled at all times. Further, the sum (Lc) of the power consumption of the pump (500) and that of the blower (230) can be controlled so that the sum (Lc) is substantially minimized. Therefore, the power consumption of the entire cooling system can be reduced.
In another embodiment of the present invention, according to the state of a load given to the liquid-cooled internal combustion engine (100), the degree of opening of the flow control valve (400) is controlled to adjust the flow rate of coolant flowing in the radiator (200). Due to the foregoing, the power consumption of the entire cooling system can be further reduced.
Incidentally, the reference numerals in the parentheses attached to the respective means show a relation with the corresponding specific means in the embodiment explained later.
The present invention will be better understood with reference to the following descriptions of the preferred embodiments of the present invention and the accompanying drawings.